var p = Math.PI;
console.log(p);

var n = prompt("请输入内容");
var c = 2 * n * p;
var d = p * n * n;


document.querySelector("#a").value = n;
document.querySelector("#b").value = c;
document.querySelector("#c").value = d;

console.log(n);
console.log(c);
console.log(d);

